Chapter 7 Flashcards
Lipids; Phospholipid
Major component of the plasma membrane is this
Hydrophohilic Heads Location
At phospholipids, are located at the internal and external surfaces, separating two aqueous regions
Hydrophobic tails Location
Located in the interior of the membrane
Who do the Phospholipids move?
They move laterally, contributing to the fluidity of membrane
Unsaturated hydrocarbon tails have…
kinks in them preventing over packing between adjacent molecules
Membrane; Lipids; Cholesterol
Reduces fluidity but prevents membrane solidification at cold temperature
What is embedded in the lipid layer?
Glycoproteins and Glycolipids
What passes through phospholipid membrane?
Small and hydrophobic
Are unsaturated fatty acids or saturated faty acids more fluid?
Unsaturated fatty acids
Hydrophobic (non-polar) molecules
Can dissolve in the lipid layer and pass through the membrane rapidly
Hydrophilic molecules
includes ion and polar molecules and do not cross the membrane easily
Membrane Protein Function
Determines most of the membranes specific functions
Asymmetrical Distribution of Protein
Membranes have distinct inside and outside faces. Determined by whether membrane is built by ER or Golgi.
Peripheral Proteins
Bound to the surface of the membrane
Integral Proteins
Penetrate the hydrophobic core
Transmembrane Proteins
Integral proteins span entirety of membrane
Hydrophobic regions of an integral protein consist of one or more stretches of non-polar amino acids, coiled into alpha helixes
Six Major Functions of Membrane Protein
Transport Enzymatic Activity Signal Transduction Cell-Cell Recognition Intercellular Joining Attachment to the cytoskeleton and extracellular matrix
Transport
Moves against gradient
Enzymatic Activity
Follows a specific sequence
Signal Transduction
Signaling Pathway. Signal binds to whole series of reactions
Cell-Cell Recognition
To bind they need to have complementary proteins. Sponge example
Intercellular Joining
Liver cells don’t mix with kidney cells
Transport Proteiins
allows passage of hydrophilic substances across the membrane. Specific for substance it moves
Channel Proteins have..
a hydrophilic channel that certain molecules or ions use as a tunnel
Channel Proteins Example
Aquaporins - Facilitate the passage of water
Carrier Proteins..
binds to molecules to change shape to shuttle them across membrane
Ion Channels..
facilitate the diffusion of ions. Gated channels open or close in response to a stimulus
Active Transport..
moves substances against their concentration gradients
Active Transport; Sodium-Potassium Pump
Maintains large excess of Na+ ions outside and less inside. Transport 3 Na outside and 2K inside.
What is the main pump in plants, fungi, and bacteria?
Proton Pump
Co-Transport
Occurs when active transport of a solute indirectly drives transport of other substances
Uniporter
Integral membrane protein binds to one molecule at a time and transports it with its concentration gradient
Symport
Integral membrane protein that transports many different molecules across membrane in the same direction
Antiport
Integral membrane protein that transports many different molecules of proteins across membrane in opposite direction
What do small molecules and water enter or leave the cell through?
Lipid bilayer or via transport proteins
How do large molecules such as polysaccharides and proteins cross the membrane?
Vesicles
Does bulk transport require energy?
Yes
Exocytosis
Transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell.
Endocytosis
Cell takes in macromolecules by forming vessicles from the plasma membrane
Three types of endocytosis?
Phagocytosis
Pinocytosis
Receptor- Mediated Endocytosis
Phagocytosis
A cell engulfs a particle in a vacuole. Vacuole fuses with a lysosome to digest in the particle
Pinocytosis (Cell Drinking)
Uptake of liquid material enclosed in vesicles form by invagination of membrane
Receptor-Mediated Endocytosis
Cells absorb metabolities/hormones/viruses by inward budding of membrane vesicles containing proteins with receptor sites specific to the molecule being absorbed
How does HIV recognize & infect
HIV must bind to the immune cell surface protein CD4 and “co-receptor” CCR5. HIV cannot enter cells individuals that lack CCR5
